Prion diseases, the frightening neuron-killing disorders that transmit via infectious proteins rather than by viruses or bacteria, rarely jump from one species to another. But just a few amino acids can tear down the barriers that stop one animal from contracting another species’ prion disease.

Bank voles are particularly susceptible to the infectious brain-wasting diseases. That susceptibility stems from the structure of one of the vole’s brain proteins, researchers from the University of California, San Francisco report April 3 in PLOS Pathogens.

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